God reveals himself through a vision to Abram that not only will He provide him an heir through actual childbirth, but that his descendants will be as numerous as the stars. 
God informs Abram that He is the one who moved his family from Ur.  As assurance that Abram will possess the land, He instructs Abram to take a bunch  of animals and kill them in a “divided” arrangement. God Himself passes through the torn animals as a smoking oven and flaming torch & promises all the land from the Nile to the Euphrates  (the entire/known world at that time).